In recent years, a valve timing control apparatus that changes opening/closing timings of an intake valve and an exhaust valve in accordance with a driving condition of an internal combustion engine (hereinafter, referred to as an “engine”). The valve timing control apparatus has a configuration in which a relative rotational phase between a drive-side rotational member which is driven by a crankshaft and a driven-side rotational member which integrally rotates with a camshaft (hereinafter, simply referred to as a “relative rotational phase”) are changed such that the opening/closing timings of the intake and exhaust valves which are opened and closed in response to the rotation of the driven-side rotational member are changed.
In general, the optimum opening/closing timings of the intake and exhaust valves vary depending on the driving condition of the engine such as starting of the engine or traveling of a vehicle. At the starting of the engine, the relative rotational phase is restricted to an intermediate lock phase between the largest retardation angle phase and the largest advance angle phase such that the opening/closing timings of the intake and exhaust valves are set to have the optimum state for the starting of the engine.
JP 2013-100836 (Reference 1) discloses a valve timing control apparatus having an intermediate lock mechanism, in which opening/closing timings are restricted to an intermediate lock phase during stopping of an engine. Since both an advance angle chamber and a retardation angle chamber need to be promptly filled with oil after the engine is started, the advance angle chamber and the retardation angle chamber communicate with each other in a locked state such that the oil supplied to the advance angle chamber is also supplied to the retardation angle chamber through a communication path. At this time, an oil supply path of the retardation angle chamber is opened to a drain and air in a hydrostatic pressure chamber, which hinders the filling of the oil, is discharged such that the filling of the oil is enhanced.
However, in the valve timing control apparatus disclosed in Reference 1, since, when the engine is stopped, the advance angle chamber and the retardation angle chamber communicate with each other and one of the advance angle chamber and the retardation angle chamber communicates with the drain, oil in the hydrostatic pressure chamber is likely to be discharged. Therefore, when the engine is started, little amount of oil remains in the hydrostatic pressure chamber and it takes time to fill the hydrostatic pressure chamber with oil in this state. In addition, when the engine is abnormally stopped such as during a stall of the engine, it is difficult to set at a lock phase in some cases. If a sufficient amount of oil is not supplied to the hydrostatic pressure chamber, a driven-side rotational member that is likely to receive cam swinging torque is greatly oscillated with respect to a drive-side rotational member and, not only it is not possible for the engine to be started but there is also a concern that, since a vane section repeatedly comes into contact with a partition section inside the apparatus, noise will be produced or the drive-side rotational member will be deformed.